The use of activated carbon for the adsorption of mercury vapor has been successfully demonstrated in various applications such as municipal waste incineration. However, there are significant differences in the concentration of mercury from waste incinerator flue gas as compared to coal-fired power plant flue gas, with the concentration of mercury from the coal-fired power plants being anywhere from 10 to 100 times lower. Also, the flue gas mercury from waste incinerators is usually in the form of mercury chloride whereas the flue gas mercury from coal-fired power plants is usually in the form of elemental mercury. Both of these differences make it more difficult to remove mercury from flue gas produced by a coal-fired power plant.
The utilization factor for activated carbon is important as it is costly. Efforts in the industry to reduce carbon costs include halogenating the carbon—usually with bromides. Also, the carbon can be ground to reduce the surface area of the carbon particles and/or injected into the system at higher temperatures, each measure taken for purposes of increasing the carbon's utilization factor. However, even with these industry efforts, compliance with more stringent emission regulations requires increased carbon injection rates.
On Dec. 16, 2011, the United States Environmental Protection Agency (U.S. EPA) issued new more stringent emission regulations for mercury and other air pollutants for both existing and new power plants. The new emission regulation for mercury produced by new power plants not firing low-rank coal is 2.0×10−4 pounds of mercury per gigawatt hour (lb mercury/GWh). Accordingly, a need exists for high performance mercury capture for purposes of achieving regulatory compliance, while minimizing additional costs associated therewith.